The present invention relates to a new and improved construction of a feeler for a monitoring apparatus, which is of the type comprising a light source for generating a monitoring signal, at least one optical conductor or guide for further conducting such signal and a light receiver, which produces a fault signal upon change of the infed monitoring signal.
For the continuous monitoring of the operating state and critical operating parameters of machines and installations there are already known to the art a large number of monitoring apparatuses. The majority of such equipment contains electrical or electronic feelers or sensors, which are connected with an electrical supply voltage and/or signal line. Although such equipment can be used for monitoring quite different parameters or magnitudes, the necessity of an electrical supply voltage or potential or a line for an electrical signal, can constitute a major drawback of these state-of-the-art systems. This is particularly true for equipment wherein the feelers thereof are installed or introduced into an explosive or explosion endangered environment.
Furthermore, there are known to the art monitoring devices, the feeler of which experiences, by virtue of the parameter to be monitored, a change in its mechanical state, which then can be gainfully employed as an output signal and further transmitted by mechanical means to a suitable evaluation device. Generally, however, such feelers only have a limited sensitivity, and it is extremely difficult to mechanically further transmit the output signal. It is for this reason that the evaluation device must be arranged as close as possible to the feeler itself.
In order to avoid the aforementioned drawbacks, there also have become known to the art monitoring apparatuses, wherein the feeler thereof contains a liquid and the output signal of which is infed, by means of a liquid or fluid line, to an evaluation device. Also this prior art equipment is associated with manifest drawbacks, there only being mentioned, by way of example, the problems associated with proper sealing and checking of the tightness of such lines or conduits and the volume and signal changes caused by the thermal dilatation of the line or conductor.
Due to the development of fiber optics there has now been afforded a transmission line or conductor, by means of which the weakest optical signals can be transmitted over large distances and/or markedly curved line paths.